I seriously don't get how an aimbot would be useful in this game. I personally don't believe that he's using an aimbot, but even if he was using aimbot, the aimbot won't be able to compensate for the player's movements, simply because there is no way to guess the direction of a person's movement.
I did some fancy shooting back in the days myself. I cannot claim to be the archer with the best skills, but I was able to hit the people who were standing still with 90-95% accuarcy back then, by playing about 50-55 hours a week. At some point I was able to guess even the direction a player is going to move very accurately too.
Seeing Quake has had about 85-90 hours in the last two weeks on Steam for the past 2-3 months I have seen him play, I think what he achieved is achievable.
I should also mention, that I have not watched the match in question.
Edit: Also about recording. I have a great GPU and a decent computer. When I turn the Shadowplay on Mount&Blade lags like hell. I am able to record a GPU consuming game such as Overwatch pretty good, without any loss of FPS but for some reason M&B causes me problems.